Torque transmission mechanisms for starter motors of internal combustion engines include a one-way clutch and a bearing for allowing rotation of a gear ring to which the starting torque is transmitted. The one-way clutch comprises an outer ring fast in rotation to a crankshaft of the internal combustion engine, and an inner ring fast in rotation to a ring gear to which starting torque is delivered by pinion mesh. A dynamic seal is provided in a place where the ring gear and the outer ring of the one-way clutch rotate relative to each other so that lubricant oil coming from the engine through lubrication holes of the ring gear does not get outside of the torque transmission mechanism.
Because the outer diameter of the outer ring of the one way clutch is usually superior to the diameter of sealing elements used for crankshafts, the linear speeds at the contact points between the sealing element and the ring way cause overheating of the seal and harm its efficiency, eventually leading to failures.
It is known to provide the torque transmission mechanism with oil projection systems to bring lubricant towards the sealing elements to prevent heating, or to use seals made of elastomeric materials such as PTFE. These solutions imply more complex assembly steps and prove to be costly.